Monitoring apparatus for energy storage device, energy storage apparatus, and a method of monitoring energy storage device

ABSTRACT

A monitoring apparatus for an energy storage device provided at a movable body and electrically connected to a load of the movable body via a switch, the monitoring apparatus comprising: a monitoring unit supplied with power from the energy storage device; wherein the monitoring unit executes monitoring operation of bringing the switch from a closed state into an opened state under a condition that the energy storage device has voltage not more than a discharge voltage threshold, and bringing the switch from the opened state into the closed state under a condition that the switch is in the opened state and the energy storage device satisfies a predetermined discharge recovery condition, and extends an interval of the monitoring operation when the movable body is parked while the switch is in the opened state, in comparison to a case where the movable body is not parked.

The present application is a Continuation Application of U.S. patentapplication Ser. No. 15/552,761, filed on Aug. 22, 2017, which is basedon International Patent Application No. PCT/JP2016/057294, filed on Mar.9, 2016, and Japanese Patent Application No. 2015-061922, filed on Mar.25, 2015, the contents of which is incorporated herein by reference inits entirety.

TECHNICAL FIELD

The present application discloses a technique relating to a monitoringapparatus for an energy storage device, an energy storage apparatus, anda method of monitoring the energy storage device.

BACKGROUND ART

There is a monitoring apparatus for an energy storage device (secondarybattery) electrically connected to a load via a switch (see PatentDocument 1 and the like). The monitoring apparatus is supplied withpower from the secondary battery to acquire voltage of the secondarybattery. The monitoring apparatus repetitively executes monitoringoperation of bringing the switch from a closed state into an openedstate when a value of the acquired voltage of the secondary batterybecomes lower than a predetermined lower limit voltage value, and thenbringing the switch from the opened state into the closed state when thevoltage value of the secondary battery becomes higher than the lowerlimit voltage value. When the voltage value of the secondary batterybecomes approximate to the lower limit voltage value, the monitoringapparatus shortens an interval of monitoring operation to promptlydetect an overdischarging state of the secondary battery and bring theswitch into the opened state for protection of the secondary battery.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP-A-2011-176940

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The conventional monitoring apparatus for the energy storage device isnot sufficiently configured to appropriately set the interval ofmonitoring operation after the switch comes into the opened state, andmay thus decrease the voltage of the energy storage device.

In order to solve the problem, the present application discloses amonitoring apparatus for an energy storage device, an energy storageapparatus, and a method of monitoring the energy storage device, whichinhibit decrease in voltage of the energy storage device.

Means for Solving the Problem

In order to achieve the object mentioned above, the present applicationdiscloses a monitoring apparatus for an energy storage device providedat a movable body and electrically connected to a load of the movablebody via a switch, the monitoring apparatus including: a monitoring unitsupplied with power from the energy storage device; in which themonitoring unit executes monitoring operation of bringing the switchfrom a closed state into an opened state under a condition that theenergy storage device has voltage not more than a discharge voltagethreshold, and bringing the switch from the opened state into the closedstate under a condition that the switch is in the opened state and theenergy storage device satisfies a predetermined discharge recoverycondition, and decreases power consumption by extending an interval ofthe monitoring operation when the load is under suspension while theswitch is in the opened state, in comparison to a case where the load isin operation.

The technique disclosed in the present application can be embodied invarious modes, such as an apparatus or a method of monitoring an energystorage device, an energy storage apparatus including the apparatus andan energy storage device, a computer program and an integrated circuitconfigured to achieve functions of the apparatus or the method, anontemporal recording medium like a CD-ROM storing the computer program,and a transmission medium like the Internet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view depicting a configuration of a batterypack according to an embodiment.

FIG. 2 is a flowchart depicting a process flow of monitoring a secondarybattery according to the embodiment.

FIG. 3 is a flowchart depicting a process flow in an opened stateaccording to the embodiment.

MODE FOR CARRYING OUT THE INVENTION

The conventional monitoring apparatus described above is notsufficiently configured to appropriately set the interval of monitoringoperation after the switch comes into the opened state. Assume that theinterval of monitoring operation is shortened even after the switchcomes into the opened state. When the secondary battery is no more inthe overdischarging state, the switch can then be brought into theclosed state to quickly recover the state where the secondary batterysupplies the load with power. Meanwhile, shortening the interval ofmonitoring operation causes increase in power consumption by themonitoring apparatus at least by power required to be supplied from thesecondary battery to the monitoring apparatus at each of the shortintervals. The voltage of the secondary battery is then furtherdecreased to be lower than minimum operating voltage or the like of themonitoring apparatus, which may thus become inoperable. Furthermore, asecondary battery having continuously decreasing voltage may not bereused. These problems are not unique to secondary batteries but areapplicable also to a monitoring apparatus for a different energy storagedevice such as a capacitor.

The present application discloses a technique to solve at least part ofthe problems mentioned above.

(1) The present application discloses a monitoring apparatus for anenergy storage device provided at a movable body and electricallyconnected to a load of the movable body via a switch, the monitoringapparatus including: a monitoring unit supplied with power from theenergy storage device; in which the monitoring unit executes monitoringoperation of bringing the switch from a closed state into an openedstate under a condition that the energy storage device has voltage notmore than a discharge voltage threshold, and bringing the switch fromthe opened state into the closed state under a condition that the switchis in the opened state and the energy storage device satisfies apredetermined discharge recovery condition, and decreases powerconsumption by extending an interval of the monitoring operation whenthe load is under suspension while the switch is in the opened state, incomparison to a case where the load is in operation. While the switch isin the opened state, it is highly required to promptly restart powersupply to the load in operation. In comparison to the case where theload is in operation, it is not highly required to promptly restartpower supply to the load under suspension. In view of this, when theload is under suspension while the switch is in the opened state, themonitoring apparatus for the energy storage device executes monitoringoperation at the longer interval with less power consumption from theenergy storage device, in comparison to the case where the load is inoperation. While the switch is in the opened state, this inhibitsdelayed restart of power supply to the load when the load is inoperation and the energy storage device satisfies the discharge recoverycondition, as well as inhibits decrease in voltage of the energy storagedevice due to power consumption by the monitoring unit while the load isunder suspension with relatively low necessity for restart of powersupply to the load.

(2) In the monitoring apparatus for the energy storage device,optionally, the energy storage device is further electrically connected,via the switch, to a charger configured to generate power with an engineof the movable body, the monitoring operation further includes bringingthe switch from the closed state into the opened state under a conditionthat the voltage of the energy storage device becomes not less than acharge voltage threshold larger than the discharge voltage threshold,and bringing the switch from the opened state into the closed stateunder a condition that the energy storage device satisfies apredetermined charge recovery condition when the switch is in the openedstate, and the monitoring unit increases power consumption by shorteningthe interval of the monitoring operation when the voltage of the energystorage device becomes not less than the charge voltage threshold tobring the switch into the opened state while the load is undersuspension, in comparison to a case where the voltage of the energystorage device becomes not more than the discharge voltage threshold tobring the switch into the opened state. When the voltage of the energystorage device becomes not less than the charge voltage threshold tobring the switch into the opened state, it is desired to decrease thevoltage of the energy storage device through discharge. In view of this,when the voltage of the energy storage device becomes not less than thecharge voltage threshold to bring the switch into the opened state whilethe load is under suspension, the monitoring apparatus for the energystorage device executes monitoring operation at the shorter intervalwith more power consumption from the energy storage device, incomparison to the case where the voltage of the energy storage devicebecomes not more than the discharge voltage threshold to bring theswitch into the opened state. When the voltage of the energy storagedevice becomes not less than the charge voltage threshold to bring theswitch into the opened state while the load is under suspension, thevoltage of the energy storage device can be decreased promptly to cancelthe state where the voltage of the energy storage device is not lessthan the charge voltage threshold.

(3) The monitoring apparatus for the energy storage device can beconfigured such that, when the voltage of the energy storage devicebecomes not less than the charge voltage threshold to bring the switchinto the opened state while the load is under suspension, powerconsumption is increased by shortening the interval of the monitoringoperation in comparison to a case where the switch is in the closedstate. When the voltage of the energy storage device becomes not lessthan the charge voltage threshold to bring the switch into the openedstate while the load is under suspension, the monitoring apparatus forthe energy storage device can promptly restart power supply to the loadat the start of operation of the load.

(4) The monitoring apparatus for the energy storage device can beconfigured such that the monitoring unit further decreases powerconsumption by extending the interval of the monitoring operation whenthe voltage of the energy storage device becomes not more than a lowvoltage threshold lower than the discharge voltage threshold while theswitch is in the opened state, in comparison to a case where the voltageof the energy storage device is larger than the low voltage threshold.The monitoring apparatus for the energy storage device can inhibitfurther decrease in voltage of the energy storage device in an exemplarycase where the switch is in the opened state for a long period.

A monitoring apparatus for an energy storage device according to thepresent embodiment will be described below with reference to thedrawings. Each of embodiments to be described hereinafter will relate toa preferred specific example of the present invention. The followingembodiments refer to numerical values, shapes, materials, constituentelements, positions and connection modes of the constituent elements,steps in a method, orders of the steps, and the like, which are merelyexemplary and are not intended to limit the present invention. In theconstituent elements according to the following embodiments, those notrecited in independent claims disclosing the most superordinate conceptwill be described as optional constituent elements. The accompanyingdrawings are schematic and are not necessarily depicted exactly.

A. Embodiments A-1. Configuration of Battery Pack

FIG. 1 is an explanatory view schematically depicting a configuration ofa battery pack 100 according to the present embodiment. The battery pack100 is provided at a movable body such as a vehicle like an automobileexemplified by a hybrid vehicle (HV) and equipped with an engine (notdepicted) as a driving source, and functions as a battery for a starter400 configured to start the engine. The battery pack 100 is charged by apower generator 200 configured to be driven (to generate power) by theengine of the movable body such as an alternator. The battery pack 100further supplies a load 500 of an electric component or the like of theautomobile with power. Specifically, the movable body includes, inaddition to the battery pack 100, the engine, the power generator 200,the starter 400, and the load 500. The battery pack 100 exemplifies anenergy storage apparatus, and the power generator 200 exemplifies acharger. Examples of the movable body include, in addition to theautomobile, various movable objects such as a motorcycle, a motorizedbicycle, an electric bicycle, and a railroad vehicle. The load describedabove is a power load consumed in the movable body used by a user suchas a passenger.

The battery pack 100 includes a secondary battery 112, a monitoringapparatus 130, a current sensor 140, a temperature sensor 150, and arelay 160.

The secondary battery 112 is electrically connected with the powergenerator 200, the starter 400 configured to start the engine, and theload 500 of the movable body, via the relay 160. In a case where therelay 160 is in a closed state, the secondary battery 112 comes into achargeable-dischargeable state where the secondary battery 112 cansupply the starter 400 and the load 500 with power and the powergenerator 200 can charge the secondary battery 112. In another casewhere the relay 160 is in an opened state, the secondary battery 112comes into a nonchargeable-nondischargeable state where the secondarybattery 112 cannot supply the starter 400 or the load 500 with power andthe power generator 200 cannot charge the secondary battery 112. Therelay 160 exemplifies a switch.

The secondary battery 112 includes a plurality of cells (not depicted)connected in series. Each of the cells is configured by a lithium ionsecondary battery or the like. The secondary battery 112 can be used ina voltage range between a predetermined upper limit voltage value VT1and a predetermined lower limit voltage value VT2. The secondary battery112 exemplifies an energy storage device.

The current sensor 140 outputs a detection signal according to chargecurrent to the secondary battery 112 by the power generator 200 ordischarge current from the secondary battery 112 to the load 500(hereinafter, collectively referred to as “charge-discharge current”).The temperature sensor 150 is configured by a thermistor or the like,and outputs a detection signal according to temperature of the secondarybattery 112.

The monitoring apparatus 130 is electrically connected to the secondarybattery 112 via a signal line, and is brought into an operable state bypower supply from the secondary battery 112. The monitoring apparatus130 includes a voltage sensor 122, a CPU 132, a memory 134, and acommunication interface (I/F) 136.

The voltage sensor 122 outputs a detection signal according to aterminal voltage value V1 of the secondary battery 112 and total voltageV2 of the secondary battery 112 and the relay 160. The memory 134 isconfigured by a RAM, a ROM, or the like, and stores various programs.The CPU 132 refers to information transmitted from the sensors andcontrol operation of the respective portions in the battery pack 100 inaccordance with the programs read out of the memory 134. For example,the CPU 132 transmits an open command signal to the relay 160 to bringthe relay 160 into the opened state, and transmits a close commandsignal to bring the relay 160 into the closed state.

The CPU 132 acquires the terminal voltage value V1 (or V2) of thesecondary battery 112 in accordance with the detection signal from thevoltage sensor 122, acquires amperage of the charge-discharge current inaccordance with the detection signal from the current sensor 140, andacquires temperature of the secondary battery 112 in accordance with thedetection signal from the temperature sensor 150. The monitoringapparatus 130 is operable at a minimum operating voltage value VT4 thatis lower than the lower limit voltage value VT2 of the secondary battery112. The communication interface 136 is configured to communicate withan external device such as an engine control unit (hereinafter, referredto as an ECU) 600. The CPU 132 exemplifies a monitoring unit.

The power generator 200 includes an AC/DC converter and a DC/DCconverter (not depicted), and outputs power used for charging thebattery pack 100.

A-2. Processing of Monitoring Secondary Battery 112

The monitoring apparatus 130 executes processing of monitoring thesecondary battery 112 under a condition that the secondary battery 112supplies power having a voltage value not less than the minimumoperating voltage value VT4. FIG. 2 is a flowchart depicting a processflow of monitoring the secondary battery. This monitoring processing isexecuted to monitor the state of the secondary battery 112 and inhibitthe secondary battery 112 from coming into an abnormal state. Assumethat the relay 160 is in the closed state at the start of monitoringprocessing.

The CPU 132 of the monitoring apparatus 130 initially determines whetheror not the load 500 is in operation (S110). The CPU 132 receives asignal indicating a state of an ignition or the like from the ECU 600,and determines in accordance with the received signal that the load 500is in operation if the ignition is ON and that the load 500 is undersuspension if the ignition is OFF. The state where the load 500 is inoperation can be expressed such that the load 500 in the movable body isbeing supplied with power or that the movable body is in operation bysupply of the power. The state where the load 500 is under suspensioncan be expressed such that the load 500 in the movable body is not beingsupplied with power or that the movable body is under suspension bystopped supply of the power.

In a case where the battery pack 100 is equipped on a start-stop systemvehicle, the CPU 132 receives, from the ECU 600, a signal indicating thestate of the ignition and a signal indicating whether or not the engineis in operation. The CPU 132 determines, in accordance with the receivedsignals, that the movable body is stopped without idling, that is, theload 500 is in operation, under a condition that the ignition is ON andthe engine is under suspension. The CPU 132 according to the presentembodiment also determines that the load 500 is in operation when themovable body (vehicle) is stopped, because the movable body is ready totravel promptly as in the case where the movable body is stopped withoutidling.

In other words, the state where the load 500 is in operation includesthe states where the movable body such as a vehicle is traveling, istraveling at high speed, is stopped without idling, or is stopped. Thestate where the load 500 is under suspension indicates a state where themovable body such as a vehicle is parked or is parked for a long period.

The CPU 132 executes first reference operation processing (S120 to S150)if the load 500 is determined as being in operation (YES in S110), andexecutes first low power consumption processing (S160 to S190) if theload 500 is determined as being under suspension, in other words, beingstopped (NO in S110).

A-2-1. First Reference Operation Processing:

In the first reference operation processing, while the relay 160 is inthe closed state, the CPU 132 of the monitoring apparatus 130 or thelike is constantly activated, consumes power from the secondary battery112, and repetitively executes operation of monitoring of the secondarybattery 112 (S130 to S150) at a reference cycle ΔT1 (e.g. several tensto several hundreds of msec). The first reference operation processingis executed when frequent operation of monitoring the secondary battery112 is relatively highly required due to frequent charge-discharge ofthe secondary battery 112 while the engine or the load 500 is inoperation, for example. The reference cycle ΔT1 exemplifies an intervalof monitoring operation.

Specifically, the CPU 132 determines whether or not the reference cycleΔT1 has elapsed from execution of the most recent monitoring operation(S120). At the start of monitoring processing, the CPU 132 determineswhether or not time corresponding to the reference cycle ΔT1 has elapsedfrom the start of the monitoring processing.

The CPU 132 stands by if the CPU 132 determines that the reference cycleΔT1 has not elapsed from execution of the most recent monitoringoperation (NO in S120), and executes monitoring operation if the CPU 132determines that the reference cycle ΔT1 has elapsed from execution ofthe most recent monitoring operation (YES in S120). Specifically, theCPU 132 acquires the terminal voltage value V, the amperage of thecharge-discharge current, and the temperature of the secondary battery112 (S130), and determines whether or not the secondary battery 112 isin an abnormal state in accordance with the acquired results (S140).

The CPU 132 according to the present embodiment determines whether ornot the secondary battery 112 is in an abnormal state of either one ofan overdischarging state, an overcharged state, an excessive currentstate, and a temperature abnormal state. In the overdischarging state,the terminal voltage value V of the secondary battery 112 is not morethan the lower limit voltage value VT2. In the overcharged state, theterminal voltage value V of the secondary battery 112 is not less thanthe upper limit voltage value VT1. In the excessive current state, theamperage of the charge-discharge current of the secondary battery 112per unit time is not less than a defined level. In the temperatureabnormal state, the temperature of the secondary battery 112 is not lessthan a defined level. The lower limit voltage value VT2 exemplifies adischarge voltage threshold and the upper limit voltage value VT1exemplifies a charge voltage threshold.

In a case where the CPU 132 determines that the secondary battery 112 isin an abnormal state (YES in S140), the CPU 132 brings the relay 160from the closed state into the opened state (S150). This brings thesecondary battery 112 into the nonchargeable-nondischargeable state toinhibit decrease in voltage of the secondary battery 112 due todischarge to the starter 400 or the load 500. In other words, thisinhibits the secondary battery 112 from coming into an abnormal state orfrom deteriorating the abnormal state for protection of the secondarybattery 112. The secondary battery 112, however, may supply themonitoring apparatus 130 with power to cause decrease in voltage of thesecondary battery 112. The CPU 132 brings the relay 160 into the openedstate, and the process flow then returns to step S110.

In another case where the CPU 132 determines that the secondary battery112 is not in an abnormal state (NO in S140), the CPU 132 keeps therelay 160 in the closed state and the process flow returns to step S110.The first reference operation processing includes operation ofmonitoring the secondary battery 112 at the reference cycle ΔT1regardless of whether the relay 160 is in the opened state or in theclosed state. Even when the relay 160 is in the opened state, chargingthe secondary battery 112 can be started promptly to return a powersource system of the vehicle to a normal state upon high output from thepower generator 200. As described above, the load 500 is determined asbeing in operation in step S110 (YES in S110) in the both cases wherethe movable body is stopped without idling and is stopped. The firstreference operation processing is thus executed in this case. While themovable body is stopped without idling and is stopped, the engine isunder suspension but a driver at a driver's seat is expected to findoverdischarge of the secondary battery 112 and execute charging workrelatively shortly.

A-2-2. First Low Power Consumption Processing:

In the first low power consumption processing, while the relay 160 is inthe closed state, the CPU 132 of the monitoring apparatus 130 istemporarily activated from a stopped state and consumes power from thesecondary battery 112 to repetitively execute operation of monitoringthe secondary battery 112 (S170 to S190) at a first low power cycle ΔT2(>ΔT1, e.g. several tens of sec) longer than the reference cycle ΔT1.The first low power consumption processing is executed when frequentoperation of monitoring the secondary battery 112 is relatively lessrequired because the secondary battery 112 has discharge amperageapproximate to a dark current amount in a case where the load 500 isunder suspension and the vehicle is parked, as to be described later. Inother words, the CPU 132 of the monitoring apparatus 130 extends theinterval of monitoring operation to suppress power consumption. Thefirst low power cycle ΔT2 exemplifies an interval of monitoringoperation.

Specifically, the CPU 132 determines whether or not the first low powercycle ΔT2 has elapsed from execution of the most recent monitoringoperation (S160). At the start of monitoring processing, the CPU 132determines whether or not time corresponding to the first low powercycle ΔT2 has elapsed from the start of the monitoring processing.

The CPU 132 stands by if the CPU 132 determines that the first low powercycle ΔT2 has not elapsed from execution of the most recent monitoringoperation (NO in S160), and executes monitoring operation if the CPU 132determines that the first low power cycle ΔT2 has elapsed from executionof the most recent monitoring operation (YES in S160). Specifically, theCPU 132 acquires the terminal voltage value V, the amperage of thecharge-discharge current, and the temperature of the secondary battery112 (S170), and determines whether or not the secondary battery 112 isin an abnormal state in accordance with the acquired results (S180). Theabnormal state is similar to that in the processing in step S140.Examples of the abnormal state have only to at least include theoverdischarging state, and the remaining examples can be different fromthose in the processing in step S140.

In a case where the CPU 132 determines that the secondary battery 112 isnot in an abnormal state (NO in S180), the CPU 132 keeps the relay 160in the closed state and the process flow returns to step S110. Inanother case where the CPU 132 determines that the secondary battery 112is in an abnormal state (YES in S180), the CPU 132 brings the relay 160from the closed state into the opened state (S190) and executesprocessing in the opened state depicted in FIG. 3 (S200).

A-2-3. Processing in Opened State:

The processing in the opened state relates to operation of monitoringthe secondary battery 112 with the relay 160 being in the opened state.The CPU 132 determines whether or not the secondary battery 112 is inthe overdischarging state (S320). In the processing in step S320, theCPU 132 can alternatively determine whether or not the abnormal statedetermined in the processing in step S180 in FIG. 2 corresponds to theoverdischarging state. In a case where the secondary battery 112 is inan abnormal state such as the overcharged state other than theoverdischarging state, the CPU 132 determines that the secondary battery112 is not in the overdischarging state (NO in S320) and executes secondreference operation processing (S380 to S410). In another case where thesecondary battery 112 is in the overdischarging state, the CPU 132determines that the secondary battery 112 is in the overdischargingstate (YES in S320) and executes second low power consumption operationprocessing (S330 to S350 and S410).

A-2-4. Second Reference Operation Processing:

In the second reference operation processing, while the relay 160 is inthe opened state, the CPU 132 of the monitoring apparatus 130 or thelike is constantly activated, consumes power from the secondary battery112, and repetitively executes operation of monitoring the secondarybattery 112 (S390 to S410) at the reference cycle ΔT1. Specifically, theCPU 132 determines whether or not the reference cycle ΔT1 has elapsedfrom execution of the most recent monitoring operation (including S130to S150 and S170 to S190) (S380). The CPU 132 stands by if the CPU 132determines that the reference cycle ΔT1 has not elapsed from executionof the most recent monitoring operation (NO in S380), and executesmonitoring operation if the CPU 132 determines that the reference cycleΔT1 has elapsed from execution of the most recent monitoring operation(YES in S380). Specifically, the CPU 132 acquires the terminal voltagevalue V, the amperage of the charge-discharge current, and thetemperature of the secondary battery 112 (S390), and determines whetheror not the abnormal state of the secondary battery 112 is canceled inaccordance with the acquired results, in other words, whether or not thesecondary battery 112 is in a normal state different from any one of theabove examples of the abnormal state (S400). In the present embodiment,the CPU 132 determines that the overcharged state of the secondarybattery 112 is canceled under a condition that the secondary battery 112does not receive voltage not less than present voltage of the secondarybattery 112 and the terminal voltage of the secondary battery 112becomes not more than charge recovery voltage (larger than the lowerlimit voltage value VT2) smaller than the upper limit voltage value VT1.This condition exemplifies a predetermined charge recovery condition.

In a case where the CPU 132 determines that the abnormal state of thesecondary battery 112 is canceled (YES in S400), the CPU 132 brings therelay 160 from the opened state into the closed state (S410). Theprocess flow then returns to step S110 in FIG. 2. In another case wherethe CPU 132 determines that the abnormal state of the secondary battery112 is not canceled (NO in S400), the CPU 132 keeps the relay 160 in theopened state and the process flow returns to step S320.

Execution of the second reference operation processing achieves thefollowing effects. As described above, the secondary battery 112 comesinto the nonchargeable-nondischargeable state when the relay 160 is inthe opened state. The secondary battery 112 does not supply the starter400 of the engine or the load 500 with power even if the ignition isturned ON. Neither the starter 400 nor the load 500 is activated in thiscase. Assume that the monitoring operation is executed at a relativelylong operation cycle when the relay 160 is in the opened state. Eventhough the secondary battery 112 comes into the normal state, it takestime for the relay 160 to come into the closed state.

In contrast, the second reference operation processing includesoperation of monitoring the secondary battery 112 at a relatively shortoperation cycle. When the secondary battery 112 comes into the normalstate, the relay 160 quickly returns into the closed state to bring thesecondary battery 112 into the chargeable-dischargeable state. Thesecondary battery 112 can thus quickly respond to a command to activatethe starter 400 and the load 500 by turning ON the ignition or the like.In a case where the secondary battery 112 is in the overcharged state orthe like while the relay 160 is in the opened state, execution ofmonitoring operation at the relatively short reference cycle ΔT1achieves quick response to a command to activate the starter 400 and theload 500. A shorter operation cycle requires more power consumption bythe monitoring apparatus 130 and accordingly decreases the terminalvoltage value V of the secondary battery 112. However, particularly whenthe secondary battery 112 is in the overcharged state, a shorteroperation cycle leads to earlier cancellation of the overcharged state.In this manner, the CPU 132 of the monitoring apparatus 130 shortens theinterval of monitoring operation to increase power consumption.

A-2-5. Second Low Power Consumption Processing:

In the second low power consumption processing, while the relay 160 isin the opened state, the CPU 132 of the monitoring apparatus 130 istemporarily activated from the stopped state and consumes power from thesecondary battery 112 to repetitively execute operation of monitoringthe secondary battery 112 (S340 to S350 and S410) at the first low powercycle ΔT2 longer than the reference cycle ΔT1. Specifically, the CPU 132determines whether or not the first low power cycle ΔT2 has elapsed fromexecution of the most recent monitoring operation (including S130 toS150 and S170 to S190) (S330).

The CPU 132 stands by if the CPU 132 determines that the first low powercycle ΔT2 has not elapsed from execution of the most recent monitoringoperation (NO in S330), and executes monitoring operation if the CPU 132determines that the first low power cycle ΔT2 has elapsed from executionof the most recent monitoring operation (YES in S330). Specifically, theCPU 132 acquires the terminal voltage value V of the secondary battery112 (S340), and determines whether or not the overdischarging state ofthe secondary battery 112 is canceled in accordance with the acquiredresult (S350). The CPU 132 according to the present embodimentdetermines that the overdischarging state of the secondary battery 112is canceled under a condition that the secondary battery 112 receivesvoltage not less than predetermined voltage or the terminal voltage ofthe secondary battery 112 becomes not less than discharge recoveryvoltage (less than the upper limit voltage value VT1) larger than thelower limit voltage value VT2. This condition exemplifies apredetermined discharge recovery condition.

Execution of the second low power consumption operation processingachieves the following effects. As described above, the secondarybattery 112 comes into the nonchargeable-nondischargeable state when therelay 160 is in the opened state. This inhibits decrease in voltage ofthe secondary battery 112 due to discharge to the starter 400 and theload 500. However, the monitoring apparatus 130 consumes power todecrease the terminal voltage value V of the secondary battery 112 andfurther deteriorate the overdischarging state. In contrast, the secondlow power consumption processing includes operation of monitoring thesecondary battery 112 at the operation cycle longer than that of thesecond reference operation processing. This inhibits decrease in voltageof the secondary battery 112 due to power consumption by the monitoringapparatus 130. In other words, when the overdischarging state brings therelay 160 into the opened state, protection of the secondary battery 112against overdischarge is prioritized over quick response to a command toactivate the starter 400 and the load 500, to inhibit the monitoringapparatus 130 from becoming inoperable and inhibit the secondary battery112 from becoming unreusable due to the terminal voltage value V of thesecondary battery 112 becoming lower than the minimum operating voltagevalue VT4 of the monitoring apparatus 130.

In a case where the CPU 132 determines that the overdischarging state ofthe secondary battery 112 is canceled (YES in S3500), the CPU 132 bringsthe relay 160 from the opened state into the closed state (S410), andthe process flow then returns to step S110 in FIG. 2. In another casewhere the CPU 132 determines that the overdischarging state of thesecondary battery 112 is not canceled (NO in S350), the CPU 132 keepsthe relay 160 in the opened state, and determines whether or not theterminal voltage value V of the secondary battery 112 is not more than alow voltage threshold VT3 in accordance with the acquired result in stepS340 (S360). The low voltage threshold VT3 is less than the lower limitvoltage value VT2 and more than the minimum operating voltage value VT4.

In a case where the CPU 132 determines that the terminal voltage value Vof the secondary battery 112 is more than the low voltage threshold VT3(NO in S360), the terminal voltage value V of the secondary battery 112still less possibly becomes not more than the minimum operating voltagevalue VT4. In this case, the process flow returns to step S320 with theoperation cycle being kept at the first low power cycle ΔT2. In anothercase where the CPU 132 determines that the terminal voltage value V ofthe secondary battery 112 is not more than the low voltage threshold VT3(YES in S360), the terminal voltage value V of the secondary battery 112highly possibly becomes not more than the minimum operating voltagevalue VT4. In this case, the process flow returns to step S320 with theoperation cycle being changed from the first low power cycle ΔT2 to alonger second low power cycle ΔT3. In other words, the CPU 132 of themonitoring apparatus 130 extends the interval of monitoring operation tosuppress power consumption. Operation of monitoring the secondarybattery 112 is thereafter executed at a longer operation cycle, to moreeffectively inhibit decrease in voltage of the secondary battery 112 dueto power consumption by the monitoring apparatus 130.

A-3. Advantages of the Present Embodiment

When the load 500 is in operation (i.e. the movable body such as avehicle is traveling, is traveling at high speed, is stopped withoutidling, or is stopped) while the relay 160 is in the opened state,prompt restart of power supply to the load 500 is highly required. In acase where the vehicle is traveling or is traveling at high speed, thepower generator 200 such as an alternator is in operation. Immediaterecovery of the relay 160 is desired when the secondary battery returnsinto the chargeable state in order to avoid uncontrollability of thevehicle due to power loss. In a different case where the vehicle isstopped without idling or is stopped, the power generator 200 such as analternator is under suspension but a passenger is boarding the vehicleand is ready to find overdischarge and execute charging work (or executecharging work within several hours). The monitoring apparatus 130 is notdischarged into an inoperable state in this case.

In comparison to a case where the load 500 is in operation, it is nothighly required to promptly restart power supply to the load 500 undersuspension (i.e. the movable body such as a vehicle is parked or isparked for a long period). In an exemplary case where the vehicle isparked, the vehicle is located at a safe place such as a parking lot.There is thus no need to immediately recover the relay 160 after therelay 160 is opened, but the relay 160 is desired to be left with powerconsumption as low as possible. In another case where the vehicle isparked for a long period, the vehicle is not used for a long period andthe secondary battery 112 is desired to delay reaching unreusable lowvoltage as much as possible. Such a state where the vehicle is not usedfor a long period can be detected by voltage of the secondary battery112 becoming lower than a predetermined level after the relay 160 isopened.

In view of this, when the load 500 is under suspension while the relay160 is in the opened state, monitoring operation according to thepresent embodiment is executed at a longer interval with less powerconsumption from the secondary battery 112 per unit time, in comparisonto the case where the load 500 is in operation.

Specifically, the second low power consumption processing (S330 to S350and S410) in the processing in the opened state depicted in FIG. 3 isexecuted at a longer interval with less power consumption from thesecondary battery 112 per unit time, in comparison to the firstreference operation processing (S120 to S150) executed after the relay160 comes into the opened state in step S150 depicted in FIG. 2. Inother words, the CPU 132 of the monitoring apparatus 130 extends theinterval of monitoring operation to suppress power consumption. Whilethe relay 160 is in the opened state, this inhibits delayed restart ofpower supply to the load 500 when the load 500 is in operation and thesecondary battery 112 becomes not in the overdischarging state, as wellas inhibits decrease in voltage of the secondary battery 112 byextending the interval of monitoring operation while the load 500 isunder suspension with relatively low necessity for restart of powersupply to the load 500.

When the secondary battery 112 comes into the overcharged state to bringthe relay 160 into the opened state, it is desired to decrease thevoltage of the secondary battery 112 through discharge. The secondarybattery 112 in the overcharged state is desired to discharge in order toreturn into a normal voltage range as soon as possible. In view of this,when the secondary battery 112 comes into the overcharged state to bringthe relay 160 into the opened state (NO in S320 in FIG. 3) while theload 500 is under suspension, monitoring operation according to thepresent embodiment is executed at a shorter interval with more powerconsumption from the secondary battery 112 per unit time, in comparisonto the case where the secondary battery 112 comes into theoverdischarging state to bring the relay 160 into the opened state (YESin S320). In other words, the CPU 132 of the monitoring apparatus 130shortens the interval of monitoring operation to increase powerconsumption. This achieves, when the secondary battery 112 comes intothe overcharged state to bring the relay 160 into the opened state whilethe load 500 is under suspension, prompter cancellation of theovercharged state of the secondary battery 112 by decreasing of theterminal voltage value V of the secondary battery 112 in comparison to acase of setting the interval of monitoring operation equally to the casewhere the secondary battery 112 is in the overdischarging state.

According to the present embodiment, in the case where the secondarybattery 112 comes into the overcharged state to bring the relay 160 intothe opened state while the load 500 is under suspension, the interval ofmonitoring operation (see S380 to S410 in FIG. 3) is shorter than theinterval of monitoring operation (see S160 to S190 in FIG. 2) in thecase where the relay 160 is in the closed state. In other words, the CPU132 of the monitoring apparatus 130 shortens the interval of monitoringoperation to increase power consumption. Power supply to the load 500can thus be restarted more promptly at the start of operation of theload 500 in comparison to a case where the interval of monitoringoperation with the relay 160 coming into the opened state due to theovercharged state of the secondary battery 112 is not less than theinterval of monitoring operation with the relay 160 being in closedstate.

B. Modification Examples

The technique disclosed in the present application is not limited to theembodiment described above, but can be modified in various modes withinthe range not departing from the purpose thereof, and can be modified inthe following exemplary manners.

The monitoring apparatus 130 according to the above embodiment includesthe single CPU 132. The monitoring apparatus 130 is not limited theretoin terms of its configuration, but can include a plurality of CPUs, caninclude hardware circuitry such as an application specific integratedcircuit (ASIC), or can include both the CPU and the hardware circuitry.

The battery pack 100 according to the above embodiment includes thesingle monitoring apparatus 130. The battery pack 100 can alternativelyinclude a plurality of monitoring apparatuses 130.

The load is not necessarily provided to an electric component but can beprovided to a motor configured to drive an electric vehicle (EV), adifferent electric instrument, or a driving source (e.g. a motor) ofindustrial machinery. The charger is not limited to an alternator butcan be installed at a charging station located outside the automobile.

The relay 160 according to the above embodiment exemplifies the switch,which is not limited to a mechanical type but can be a semiconductorswitch or the like. The switch is not necessarily incorporated in thebattery pack 100 but can alternatively be provided outside the batterypack 100. The switch can still alternatively be configured by aplurality of relays connected parallelly.

The energy storage device according to the above embodiment isexemplified by a lithium ion secondary battery. The energy storagedevice is not limited thereto, but examples thereof include a differentsecondary battery, a primary battery, and a capacitor. The energystorage device is not limited to an assembled battery having a pluralityof cells, but can be a battery having a single cell.

The examples of the abnormal state determined in step S140 in FIG. 2have only to include at least the overdischarging state. The examples ofthe abnormal state include, in addition to the overcharged state, theexcessive current state, and the temperature abnormal state, an abnormalstate of internal resistance, open circuit voltage (OCV), an SOC, or thelike of the energy storage device. The processing in step S140 canalternatively include determining whether or not the secondary battery112 possibly comes into an abnormal state. For example, the CPU 132 canalternatively determine whether or not the terminal voltage value V ofthe secondary battery 112 is not more than the discharge voltagethreshold slightly higher than the lower limit voltage value VT2. TheCPU 132 can still alternatively determine whether or not the terminalvoltage value V of the secondary battery 112 is not less than the chargevoltage threshold slightly lower than the upper limit voltage value VT1.

In the processing in the opened state, the CPU 132 can alternativelyskip the processing in step S320 and execute the second low powerconsumption processing (S330 to S350 and S410) regardless of the type ofthe abnormal state. In the processing in the opened state, the processflow of the CPU 132 can return to step S320 by skipping the processingin steps S360 and S370 if the CPU 132 determines that theoverdischarging state is not canceled (NO in S350).

In the processing in the opened state, the CPU 132 can execute thesecond low power consumption operation processing also in the case wherethe secondary battery 112 is in the excessive current state, thetemperature abnormal state, or the like, in addition to theoverdischarging state. When the vehicle is parked or is parked for along period, the vehicle is located at a safe place such as a parkinglot or is not used for a long period. There is thus no need toimmediately recover after the relay 160 is opened, and the secondarybattery 112 is desired to delay reaching unusable low voltage as much aspossible.

The first reference operation processing and the second referenceoperation processing can be different from each other in terms of thecycle of monitoring operation and the power consumption level.Furthermore, first low power consumption operation processing and thesecond low power consumption operation processing can be different fromeach other in terms of the cycle of monitoring operation and the powerconsumption level.

The load 500 can be defined as being under suspension while the movablebody such as a vehicle is stopped without idling or is stopped.Specifically, the load 500 can be assumed to be in operation when themovable body is traveling or is traveling at high speed, and the load500 can be assumed to be under suspension when the movable body isstopped without idling, is stopped, is parked, or is parked for a longperiod.

The CPU 132 can alternatively be configured to execute monitoringoperation at a longer interval (the first low power cycle ΔT2 or thesecond low power cycle ΔT3) as the movable body is parked for a longerperiod. In other words, the CPU 132 can be configured to executemonitoring operation at a longer cycle when the movable body is parkedfor a long period, in comparison to a case where the movable body isparked for a short period.

Table 1 below collectively indicates relations between the voltagevalues described above and the intervals of monitoring operation. Inthis table, VT1 denotes the predetermined upper limit voltage value, VT2denotes the predetermined lower limit voltage value, VT4 denotes theminimum operating voltage value allowing the monitoring apparatus 130 tobe operable, and VT3 denotes the low voltage threshold lower than VT2and higher than VT4. These values satisfy the relation VT1>VT2>VT3>VT4.Furthermore, ΔT1 denotes the reference cycle, ΔT2 denotes the first lowpower cycle, and ΔT3 denotes the second low power cycle. These valuessatisfy the relation ΔT1<ΔT2<ΔT3.

TABLE 1 Interval of Terminal voltage monitoring State of load value Voperation Remarks In operation No condition ΔT1 for V Under V ≥ VT1 ΔT1Overcharged state suspension VT1 > V > VT2  ΔT2 Charge or dischargerecovery condition VT2 ≥ V > VT3 ΔT2 Overdischarging state VT3 ≥ V > VT4ΔT3

The interval of monitoring operation can be set to ΔT2 when V=VT1 isestablished, or the interval can be set to ΔT2 when V=VT3 isestablished. Table 1 does not indicate a case where V is not more thanVT4 as the monitoring apparatus 130 is inoperable in the range.

DESCRIPTION OF REFERENCE SIGNS

-   -   100: battery pack    -   112: secondary battery    -   122: voltage sensor    -   130: monitoring apparatus    -   132: CPU    -   134: memory    -   136: communication interface    -   140: current sensor    -   150: temperature sensor    -   160: relay    -   200: power generator    -   400: starter    -   500: load    -   600: ECU    -   ΔT1: reference cycle    -   ΔT2: first low power cycle    -   ΔT3: second low power cycle    -   V: terminal voltage value    -   VT1: upper limit voltage value    -   VT2: lower limit voltage value    -   VT3: low voltage threshold    -   VT4: minimum operating voltage value

The invention claimed is:
 1. A monitoring apparatus for an energystorage device provided at a movable body and electrically connected toa load of the movable body via a switch, the monitoring apparatuscomprising: a monitoring unit supplied with power from the energystorage device, wherein the monitoring unit executes a monitoringoperation of bringing the switch from a closed state into an openedstate under a condition that the energy storage device has a voltage notmore than a discharge voltage threshold, and bringing the switch fromthe opened state into the closed state under a condition that the switchis in the opened state and the energy storage device satisfies apredetermined discharge recovery condition, and extends an interval ofthe monitoring operation when the movable body is parked while theswitch is in the opened state, in comparison to a case where the movablebody is not parked.
 2. The monitoring apparatus for the energy storagedevice according to claim 1, wherein the energy storage device isfurther electrically connected, via the switch, to a charger configuredto generate power with an engine of the movable body, the monitoringoperation further includes bringing the switch from the closed stateinto the opened state under a condition that the voltage of the energystorage device becomes not less than a charge voltage threshold largerthan the discharge voltage threshold, and bringing the switch from theopened state into the closed state under a condition that the energystorage device satisfies a predetermined charge recovery condition whenthe switch is in the opened state, and the monitoring unit increasespower consumption by shortening the interval of the monitoring operationwhen the voltage of the energy storage device becomes not less than thecharge voltage threshold to bring the switch into the opened state whilethe movable body is parked, in comparison to a case where the voltage ofthe energy storage device becomes not more than the discharge voltagethreshold to bring the switch into the opened state.
 3. The monitoringapparatus for the energy storage device according to claim 2, whereinwhen the voltage of the energy storage device becomes not less than thecharge voltage threshold to bring the switch into the opened state whilethe movable body is parked, power consumption is increased by shorteningthe interval of the monitoring operation, in comparison to a case wherethe switch is in the closed state.
 4. The monitoring apparatus for theenergy storage device according to claim 1, wherein the monitoring unitfurther decreases power consumption by extending the interval of themonitoring operation when the voltage of the energy storage devicebecomes not more than a low voltage threshold lower than the dischargevoltage threshold while the switch is in the opened state, in comparisonto a case where the voltage of the energy storage device is larger thanthe low voltage threshold.
 5. The monitoring apparatus for the energystorage device according to claim 2, wherein the monitoring unit furtherdecreases power consumption by extending the interval of the monitoringoperation when the voltage of the energy storage device becomes not morethan a low voltage threshold lower than the discharge voltage thresholdwhile the switch is in the opened state, in comparison to a case wherethe voltage of the energy storage device is larger than the low voltagethreshold.
 6. The monitoring apparatus for the energy storage deviceaccording to claim 3, wherein the monitoring unit further decreasespower consumption by extending the interval of the monitoring operationwhen the voltage of the energy storage device becomes not more than alow voltage threshold lower than the discharge voltage threshold whilethe switch is in the opened state, in comparison to a case where thevoltage of the energy storage device is larger than the low voltagethreshold.
 7. An energy storage apparatus comprising: an energy storagedevice; and the monitoring apparatus for the energy storage deviceaccording to claim
 1. 8. An energy storage apparatus comprising: anenergy storage device; and the monitoring apparatus for the energystorage device according to claim
 2. 9. An energy storage apparatuscomprising: an energy storage device; and the monitoring apparatus forthe energy storage device according to claim
 3. 10. An energy storageapparatus comprising: an energy storage device; and the monitoringapparatus for the energy storage device according to claim
 4. 11. Theenergy storage apparatus according to claim 7, further comprising: aswitch disposed between the load of the movable body and the energystorage device.
 12. The energy storage apparatus according to claim 8,further comprising: a switch disposed between the load of the movablebody and the energy storage device.
 13. The energy storage apparatusaccording to claim 9, further comprising: a switch disposed between theload of the movable body and the energy storage device.
 14. The energystorage apparatus according to claim 10, further comprising: a switchdisposed between the load of the movable body and the energy storagedevice.
 15. A method of monitoring an energy storage device provided ata movable body and electrically connected to a load of the movable bodyvia a switch, the method executed by a monitoring apparatus for theenergy storage device and comprising: executing a monitoring operationof bringing the switch from a closed state into an opened state under acondition that the energy storage device has a voltage not more than adischarge voltage threshold, and bringing the switch from the openedstate into the closed state under a condition that the switch is in theopened state and the energy storage device satisfies a predetermineddischarge recovery condition; and decreasing power consumption byextending an interval of the monitoring operation when the movable bodyis parked while the switch is in the opened state, in comparison to acase where the movable body is not parked.
 16. The method of monitoringthe energy storage device according to claim 15, wherein the energystorage device is further electrically connected, via the switch, to acharger configured to generate power with an engine of the movable body,the monitoring operation further includes bringing the switch from theclosed state into the opened state under a condition that the voltage ofthe energy storage device becomes not less than a charge voltagethreshold larger than the discharge voltage threshold, and bringing theswitch from the opened state into the closed state under a conditionthat the energy storage device satisfies a predetermined charge recoverycondition when the switch is in the opened state, and the monitoringapparatus increases power consumption by shortening the interval of themonitoring operation when the voltage of the energy storage devicebecomes not less than the charge voltage threshold to bring the switchinto the opened state while the movable body is parked, in comparison toa case where the voltage of the energy storage device becomes not morethan the discharge voltage threshold to bring the switch into the openedstate.
 17. The method of monitoring apparatus the energy storage deviceaccording to claim 16, wherein when the voltage of the energy storagedevice becomes not less than the charge voltage threshold to bring theswitch into the opened state while the movable body is parked, powerconsumption is increased by shortening the interval of the monitoringoperation, in comparison to a case where the switch is in the closedstate.
 18. The method of monitoring the energy storage device accordingto claim 15, wherein the monitoring apparatus further decreases powerconsumption by extending the interval of the monitoring operation whenthe voltage of the energy storage device becomes not more than a lowvoltage threshold lower than the discharge voltage threshold while theswitch is in the opened state, in comparison, to a case where thevoltage of the energy storage device is larger than the low voltagethreshold.